Optical disk apparatus

ABSTRACT

An optical disk apparatus which subsidiarily moves a feed at kick seek, thereby performing a tracking control is constituted to calculate a reference feed shifting amount and a compensation amount of the feed shifting on the basis of a lens offset just before starting of the kick seek and the number of tracks on an optical disk by which the lens is moved by the kick seek, further add/subtract the compensation amount to/from the reference feed shifting amount on the basis of the direction of the kick seek, thereby calculating a feed shifting amount, and subsidiarily move the feed by the feed shifting amount in concurrence with the kick seek. Thereby, tracking after the kick seek can be performed stably.

TECHNICAL FIELD

The present invention relates to an optical disk apparatus typified by aCD-ROM drive and, more particularly, to an optical disk apparatus whichsubsidiarily moves a feed at kick seek when data is read from anarbitrary position on an optical disk surface, thereby performing atracking control.

BACKGROUND ART

In recent years, standard mounting of an optical disk apparatus on apersonal computer has been rapidly progressed, and accordingly theoptical disk apparatus as well as a hard disk drive have becomeindispensable to the personal computer. Initially the CD-ROM drive hasconstituted the majority of the optical disk apparatus, while nowadays aDVD-ROM drive having a larger capacity than the CD-ROM drive, or awritable or rewritable CD-R/CD-RW drive is normally mounted on thepersonal computer, and further a DVD-R or DVD-RAM drive comes on amarket. As described above, the efficiency and function of the opticaldisk apparatus has been enhanced continuingly.

FIG. 10 is a schematic diagram illustrating a whole conventional opticaldisk apparatus. In the figure, numeral 11 denotes a disk, numeral 12denotes a spindle motor, numeral 13 denotes a pickup, numeral 14 denotesa lens, numeral 15 denotes a feed, numeral 16 denotes a feed motor,numeral 17 denotes a driver IC, numeral 18 denotes an analog front endIC, numeral 19 denotes a digital signal processor IC, numeral 20 denotesa decoder, numeral 21 denotes a CPU, and numeral 22 denotes a host.

FIG. 11 is an explanation drawing illustrating a constitution of apickup of an optical disk apparatus. In the figure, numeral 13 denotes apickup, numeral 14 denotes a lens, and numerals 25 and 26 denote wiresfor supporting the lens 14 in a housing of the pickup 13.

Next, a data reading operation of the optical disk apparatus will bedescribed.

The disk 11 is controlled by the spindle motor 12 for rotating at aconstant linear velocity or a constant angular velocity. The pickup 13,moving from the inner track side to the outer track side in the radialdirection of the disk 11, applies a laser beam to the surface of thedisk 11 and receives light reflected therefrom, thereby reading data onthe disk 11. Data called pit are spirally recorded on the disk 11, andthe number of the spirals in the radial direction is referred to as thenumber of tracks. To accurately read the data on the disk 11, the pickup13 drives the lens 14 in a direction perpendicular to the disk surface,thereby focusing the laser beam onto the disk 11. Further, the pickup 13receives the reflected light from the disk 11 and detects a deviationfrom the center of a track. A tracking control for moving the lens 14horizontally in the radial direction of the disk 11 is performed so thatthe deviation is eliminated and the laser beam is applied to the centerof the track. When the lens 14 is a prescribed distance or more apartfrom the center of the housing, the feed 15 to which the pickup 13 isfixed is moved to return the lens 14 to the center of the housing. Afocus and tracking control of the lens 14 is performed by the driver 17according to a command of the CPU 21, and the data which are accuratelyread are transferred to the host 22 via the analog front end IC 18, thedigital signal processor IC 19 and the decoder IC 20.

Next, influence which are exerted by the deviation of the lens in thepickup upon the data reading operation will be described with referenceto FIG. 12.

FIG. 12 is a diagram for explaining the influences exerted by thedeviation of the lens in the pickup upon the data reading. In thefigure, numeral 11 denotes the disk, numerals 32 and 33 denote lenses,numeral 34 denotes a laser, and numeral 35 denotes a photo acceptanceelement.

The lens 32, which is located at the center in the pickup, refractslight from the laser 34, thereby obtaining a focus on the disk 11. Then,the disk 11 returns a reflected light to the photo acceptance element35. However, the lens 33, which is in a position deviated from thecenter in the pickup, may cause the reflected light from the disk 11 tobe out of the photo acceptance unit 35, as shown by a dotted line inFIG. 12. In this case, a tracking servo cannot generate a signal fordetecting a position on the basis of the reflected light from the disk11. Therefore, the optical disk apparatus cannot read data accuratelydue to the deviation of the lens, resulting in unstable tracking.

Next, a seek operation for accurately performing the data readingoperation will be described.

The optical disk apparatus performs the seek operation to read dataaccurately.

In this operation, when the pickup 13 is moved to an arbitrary positionon the disk 11 in accordance with a command from the outside such as thehost 22, the number of tracks from the current read position to a targetposition is obtained by calculation, and the pickup 13 or the lens 14 ismoved by the obtained number of tracks, thereby adjusting the readingposition. This seek operation has two kinds of operation, i.e., feedseek and kick seek. The feed seek is one which moves the feed 15 to movethe pickup 13 to a target position, which is employed for a relativelylong-distance movement. The kick seek is one which moves the lens 14after the feed seek in the housing of the pickup 13 to reach a track ina target position, which is employed for a relatively short-distancemovement.

Here, the feed seek will be described with reference to FIGS. 11 and 13.

FIGS. 13( a) and 13(b) are diagrams for explaining positional changes ofthe lens at the feed seek, FIG. 13( a) illustrating a case where thefeed is moved in an inner radial direction and FIG. 13( b) illustratinga case where the feed is moved in an outer radial direction. In thefigure, numeral 13 denotes a pickup, numeral 14 denotes a lens, andnumeral 15 denotes a feed.

The conventional optical disk apparatus is quite vulnerable to externalvibrations or the like, because the lens 14 is supported by wires 25 and26 in the pickup 13 as shown in FIG. 11. However, since the feed seekmay be likened a kind of external vibrations, the lens 14 may beadversely deviated from the center of the pickup. 13 as shown in FIG. 13when the feed seek is excessively accelerated or decelerated.

Next, the kick seek will be described with reference to FIGS. 14 and 15.

FIGS. 14( a) and 14(b) are diagrams for explaining positional changes ofthe lens at the kick seek, FIG. 14( a) illustrating a state before thekick seek and FIG. 14( b) illustrating a state after the kick seek. Inthe figure, numeral 13 denotes a pickup and numeral 14 denotes a lens.

In the conventional optical disk apparatus, when the lens 14 performsthe kick seek from the central position in the pickup 13, the lens 14 isdeviated in the pickup 13 by the kick seek as shown by a dotted line inFIG. 14( a) unless the feed 15 is subsidiarily moved. However, since thedriver 17 drives the feed motor 16, thereby subsidiarily moving the feed15 by a reference feed shifting amount F0, the lens 14 is located at thecenter in the pickup 13 after the kick seek. This reference feedshifting amount F0 is calculated by the CPU 21, and its calculatingmeans will be described hereinafter.

FIG. 15 is a block diagram illustrating a means for calculating the feedshifting amount in the CPU of the conventional optical disk apparatus.In the figure, numeral 3 denotes a number-of-kick-seek-trackscalculating means for calculating the number of tracks by which the lensis moved at the kick seek, and numeral 5 denotes a reference feedshifting amount calculating means for calculating the quantity by whichthe feed is subsidiarily moved at the kick seek.

In the figure, the number-of-kick-seek-tracks calculating means 3calculates the number of kick seek tracks on the basis data of thecurrent position and a target position of the lens 14, just before thekick seek starts, which corresponds to a moving distance of the lens 14at the kick seek. The reference feed shifting amount calculating means 5calculates the reference feed shifting amount on the basis of the numberof kick seek tracks, and outputs the calculated amount to the driver 17.

Problems of the conventional optical disk apparatus will be describedwith reference to FIGS. 16 and 17.

FIGS. 16( a) and 16(b) are diagrams for explaining problems at the kickseek from a state where the lens is deviated, FIG. 16( a) illustrating astate before the kick seek and FIG. 16( b) illustrating a state afterthe kick seek. In the figure, numeral 13 denotes a pickup and numeral 14denotes a lens.

In the conventional optical disk apparatus, when the kick seek isperformed from a state where the lens 14 is deviated in the pickup 13,the lens 14 is located at the center in the pickup 13 as shown by adotted line in FIG. 16( a). Further, when the feed is subsidiarily movedby the reference feed shifting amount F0, the lens 14 is returned to thedeviated state before the kick seek again, as shown in FIG. 16( b). Asdescribed above, in the conventional optical disk apparatus, even whenthe kick seek is performed from a state where the lens 14 is deviated inthe pickup 13 and the feed is subsidiarily moved by the reference feedshifting amount F0, the deviated state of the lens 14 as before the kickseek is merely retained and the deviation of the lens 14 is not at alleliminated also after the kick seek as shown in FIG. 16( b).

FIGS. 17( a) and 17(b) are diagrams for explaining problems at kick seekfrom a state where the feed keeps moving by the inertia of feed seek,FIG. 17( a) illustrating a state after the feed seek and FIG. 17( b)illustrating a state after the kick seek. In the figure, numeral 13denotes a pickup and numeral 14 denotes a lens.

In the conventional optical disk apparatus, even when the lens 14 islocated at the central position of the pickup 13 after the feed seek,when the kick seek is performed from a state where the feed keeps movingby the inertia of the feed seek before the kick seek and the feed issubsidiarily moved for the reference feed shifting amount, the lens 14is deviated in the pickup 13 as shown in FIG. 17( b). When accelerationor deceleration of the feed seek is excessive, the inertia of the feedseek is increased, whereby this is easier to occur.

The present invention is made to solve the above-mentioned problems andhas for its object to provide an optical disk apparatus in which a lensis located at the center in a housing of a pickup after the kick seek,thereby enabling to perform subsequent tracking stably.

DISCLOSURE OF THE INVENTION

To solve the above-described problems, according to a first aspect ofthe present invention, there is provided an optical disk apparatus whichsubsidiarily moves a feed at kick seek when data is read from anarbitrary position on an optical disk surface, thereby performing atracking control, comprising: a pre-kick-seek offset calculating meansfor calculating an offset of a lens on the basis of a position of thelens in a pickup just before the kick seek starts; a kick seek directionjudging means for judging whether a direction of the kick seek is aninner radial direction or an outer radial direction on the basis of acurrent position and a target position of the lens just before the kickseek starts; a number-of-kick-seek-tracks calculating means forcalculating the number of tracks on an optical disk by which the lens ismoved by the kick seek; a reference feed shifting amount calculatingmeans for calculating a reference feed shifting amount on the basis ofthe number of tracks calculated by the number-of-kick-seek-trackscalculating means; a compensation amount calculating means forcalculating a compensation amount by multiplying the offset calculatedby the pre-kick-seek offset calculating means by a compensationcoefficient; a feed shifting amount calculating means for adding thecompensation amount and the reference feed shifting amount when thedirection is judged to be the inner radial direction by the kick seekdirection judging means, and subtracting the compensation amount fromthe reference feed shifting amount when it is judged to be the outerradial direction, thereby calculating a feed shifting amount; and acontrol means for subsidiarily moving the feed by the feed shiftingamount in concurrence with the kick seek.

According to the invention, the lens is located at the center in ahousing of the pickup after the kick seek, whereby subsequent trackingcan be stably performed.

According to a second aspect of the present invention, there is providedan optical disk apparatus which subsidiarily moves a feed at kick seekwhen data is read from an arbitrary position on an optical disk surface,thereby performing a tracking control, comprising: anumber-of-feed-seek-tracks calculating means for calculating the numberof tracks on an optical disk by which a lens is moved by feed seekbefore the kick seek; a kick seek direction judging means for judgingwhether a direction of the kick seek is an inner radial direction or anouter radial direction on the basis of a current position and a targetposition of the lens just before the kick seek starts; anumber-of-kick-seek-tracks calculating means for calculating the numberof tracks on an optical disk by which the lens is moved by the kickseek; a reference feed shifting amount calculating means for calculatinga reference feed shifting amount on the basis of the number of trackscalculated by the number-of-kick-seek-tracks calculating means; acompensation amount calculating means for calculating a compensationamount by multiplying the number of tracks calculated by thenumber-of-feed-seek-tracks calculating means by a compensationcoefficient; a feed shifting amount calculating means for adding thecompensation amount and the reference feed shifting amount when thedirection is judged to be the inner radial direction by the kick seekdirection judging means, and subtracting the compensation amount fromthe reference feed shifting amount when it is judged to be the outerradial direction, thereby calculating a feed shifting amount; and acontrol means for subsidiarily moving the feed by the feed shiftingamount in concurrence with the kick seek.

According to the invention, even when the movement of the feed seekremains as the inertia, the lens is located at the center in a housingof the pickup after the kick seek, whereby subsequent tracking can beperformed stably.

According to a third aspect of the present invention, there is providedan optical disk apparatus which subsidiarily moves a feed at kick seekwhen data is read from an arbitrary position on an optical disk surface,thereby performing a tracking control, comprising: a post-feed-seekoffset calculating means for calculating an offset of a lens on thebasis of a position of the lens in a pickup just after an end of feedseek before the kick seek; a pre-kick-seek offset calculating means forcalculating an offset of the lens on the basis of the position of thelens in the pickup just before the kick seek starts; a kick seekdirection judging means for judging whether a direction of the kick seekis an inner radial direction or an outer radial direction on the basisof a current position and a target position of the lens just before thekick seek starts; a number-of-kick-seek-tracks calculating means forcalculating the number of tracks on an optical disk by which the lens ismoved by the kick seek; a reference feed shifting amount calculatingmeans for calculating a reference feed shifting amount on the basis ofthe number of tracks calculated by the number-of-kick-seek-trackscalculating means; a compensation amount calculating means forcalculating a compensation amount by multiplying a difference betweenthe offset calculated by the pre-kick-seek offset calculating means andthe offset calculated by the post-feed-seek offset calculating means, bya compensation coefficient; a feed shifting amount calculating means foradding the compensation amount and the reference feed shifting amountwhen the direction is judged to be the inner radial direction by thekick seek direction judging means, and subtracting the compensationamount from the reference feed shifting amount when it is judged to bethe outer radial direction, thereby calculating a feed shifting amount;and a control means for subsidiarily moving the feed by the feedshifting amount in concurrence with the kick seek.

According to the invention, even when the movement of the feed seekremains as the inertia, the lens is located at the center in a housingof the pickup after the kick seek, whereby subsequent tracking can beperformed stably.

According to a fourth aspect of the present invention, in the opticaldisk apparatus as defined in any of the first through third aspects, anabsolute value of the compensation amount is smaller than an absolutevalue of the reference feed shifting amount.

According to the invention, the lens does not move in a directionopposite to the direction along which the pickup moves at the kick seekand the relative velocity between the lens and the pickup is reduced,thereby realizing more stable tracking.

According to a fifth aspect of the present invention, in the opticaldisk apparatus as defined in any of the first through third aspects, thecompensation coefficient is proportional to the number of trackscalculated by the number-of-kick-seek-tracks calculating means.

According to the invention, when the number of kick seek tracks is smalland the seek operation is continued, the feed shifting amount isadjusted according to the number of kick seek tracks, and vibrations orresonance of the mechanism caused by subsidiarily moving the feed morethan the lens deviation by the kick seek are suppressed, therebyrealizing more stable tracking.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a means for calculating a feedshifting amount of an optical disk apparatus according to a firstembodiment of the present invention.

FIGS. 2( a)–2(c) are diagrams for explaining a case where kick seek isperformed in an outer radial direction from a state where a lens isdeviated in an inner radial direction in the first embodiment of theinvention.

FIGS. 3( a)–3(c) are diagrams for explaining a case where kick seek isperformed in an inner radial direction from a state where the lens isdeviated in the inner radial direction in the first embodiment of theinvention.

FIG. 4 is a block diagram illustrating a means for calculating a feedshifting amount of an optical disk apparatus according to a secondembodiment of the present invention.

FIGS. 5( a)–5(c) are diagrams for explaining a case where kick seek isperformed in an outer radial direction from a state where feed seek inthe outer radial direction is ended in the second embodiment of theinvention.

FIGS. 6( a)–6(c) are diagrams for explaining a case where kick seek isperformed in an inner radial direction from a state where feed seek inan outer radial direction is ended in the second embodiment of theinvention.

FIG. 7 is a block diagram illustrating a means for calculating a feedshifting amount of an optical disk apparatus according to a thirdembodiment of the present invention.

FIGS. 8( a)–8(c) are diagrams for explaining a case where kick seek isperformed in an outer radial direction from a state where a movementresulting from inertia remains even when feed seek in the outer radialdirection is ended in the third embodiment of the invention.

FIGS. 9( a)–9(c) are diagrams for explaining a case where kick seek isperformed in an inner radial direction from a state where a movementresulting from inertia remains even when feed seek in an outer radialdirection is ended in the third embodiment of the invention.

FIG. 10 is a schematic diagram illustrating a whole conventional opticaldisk apparatus.

FIG. 11 is a diagram for explaining a structure of a pickup of anoptical disk apparatus.

FIG. 12 is a diagram for explaining influences which are exerted by adeviation of a lens in a pickup upon data reading.

FIGS. 13( a) and 13(b) are diagrams for explaining positional changes ofa lens at feed seek.

FIGS. 14( a) and 14(b) are diagrams for explaining positional changes ofa lens at kick seek.

FIG. 15 is a block diagram illustrating a means for calculating a feedshifting amount in a CPU of the conventional optical disk apparatus.

FIGS. 16( a) and 16(b) are diagrams for explaining problems of kick seekfrom a state where a lens is deviated.

FIGS. 17( a) and 17(b) are diagrams for explaining problems of kick seekfrom a state where a feed keeps moving by the inertia of feed seek.

BEST MODE TO EXECUTE THE INVENTION

(Embodiment 1)

FIG. 1 is a block diagram illustrating a means for calculating a feedshifting amount of an optical disk apparatus according to a firstembodiment of the present invention. In the figure, numeral 1 denotes apre-kick-seek offset calculating means for calculating an offset of alens before kick seek, numeral 2 denotes a kick seek direction judgingmeans for judging a direction of kick seek, numeral 4 denotes acompensation amount calculating means for calculating the amount ofcompensation of a reference feed shifting amount, and numeral 6 denotesa feed shifting amount calculating means for calculating the amount of asubsidiary movement of a feed, and these are implemented by software ona CPU.

A number-of-kick-seek-tracks calculating means 3 and a reference feedshifting amount calculating means 5 in the optical disk apparatusaccording to the first embodiment are the same as those denoted by thesame reference numerals in the conventional optical disk apparatus.

Next, the operation will be described.

Just before kick seek starts, the pre-kick-seek offset calculating means1 receives data of the quantity of deviation of a lens 14 from thecenter of a housing of a pickup 13 from the analog front end IC 18,A/D-converts the data to calculate an offset before kick seek, andoutputs the calculated offset to the compensation amount calculatingmeans 4. Simultaneously, the kick seek direction judging means 2 judgeswhether the direction of kick seek is an inner radial direction or anouter radial direction on the basis of the current position and a targetposition of the lens 14, and outputs the obtained result to the feedshifting amount calculating means 6. On the other hand, just before thekick seek starts, the number-of-kick-seek-tracks calculating means 3calculates the number of kick seek tracks that corresponds to a movingdistance of the lens 14 on the basis of the current position and thetarget position of the lens 14, and outputs the obtained number to thereference feed shifting amount calculating means 5 and the compensationamount calculating means 4. The reference feed shifting amountcalculating means 5 calculates a reference feed shifting amount on thebasis of the number of kick seek tracks and outputs the obtained amountto the feed shifting amount calculating means 6. The compensation amountcalculating means 4 calculates a compensation amount by multiplying acoefficient which is proportional to the number of kick seek tracks bythe offset before kick seek, and outputs the obtained compensationamount to the feed shifting amount calculating means 6. The feedshifting amount calculating means 6 adds the compensation amount and thereference feed shifting amount in the case of kick seek in the innerradial direction, while subtracting the compensation amount from thereference feed shifting amount in the case of kick seek in the outerradial direction, thereby calculating a feed shifting amount. When thecalculated feed shifting amount is smaller than 0, the feed shiftingamount is outputted as 0.

Therefore, assuming that “F” is the feed shifting amount, “F0” is thereference feed shifting amount, “offset” is the offset before kick seek,“α” is the coefficient (α=γT), “γ” is the coefficient, “T” is the numberof kick seek tracks, the feed shifting amount has no polarity, and thepolarity of the offset is “+” in the inner radial direction and “−” inthe outer radial direction, the feed shifting amount at kick seek isdecided in the CPU 21 as a whole by the following expressions:

-   -   In the case of kick seek in the inner radial direction        -   F=F 0+α offset (F=0, when F 0+α offset<0)    -   In the case of kick seek in the outer radial direction        -   F=F 0−α offset (F=0, when F 0−α offset<0)

Next, the functions will be described with reference to FIGS. 2 and 3.

FIGS. 2( a)–2(c) are diagrams for explaining a case where kick seek isperformed in the outer radial direction from a state where the lens isdeviated in the inner radial direction, in which FIG. 2( a) shows astate before the kick seek, FIG. 2( b) shows a state after kick seek bythe reference feed shifting amount, and FIG. 2( c) shows a state afterkick seek by the feed shifting amount.

In the figure, when the amount of a subsidiary movement of the feed atthe kick seek is the reference feed shifting amount which is calculatedon the basis of the number of kick seek tracks, the deviation of thelens 14 is not at all eliminated as shown in FIG. 2( b). In the opticaldisk apparatus according to the first embodiment, the feed shiftingamount F is smaller than the reference feed shifting amount F0 (0<F<F0).Accordingly, the amount of the lens movement with respect to the feedshifting amount of kick seek is large, whereby the lens 14 is located atthe center of the pickup 13 as shown in FIG. 2( c). The same thing canbe said of a case where the kick seek is performed in the inner radialdirection from a state where the lens 14 is deviated in the outer radialdirection.

FIGS. 3( a)–3(c) are diagrams for explaining a case where kick seek isperformed in the inner radial direction from a state where the lens isdeviated in the inner radial direction, in which FIG. 3( a) shows astate before the kick seek, FIG. 3( b) shows a state after kick seek bythe reference feed shifting amount, and FIG. 3( c) shows a state afterkick seek by the feed shifting amount.

In the figure, when the amount of a subsidiary movement of the feed atthe kick seek is the reference feed shifting amount which is calculatedon the basis of the number of kick seek tracks, the deviation of thelens 14 is not at all eliminated as shown in FIG. 3( b). On the otherhand, in the optical disk apparatus according to the first embodiment,the feed shifting amount F is larger than the reference feed shiftingamount F0 (0<F0<F). Thus, the lens 14 is located at the center of thepickup 13 as shown in FIG. 3( c). The same thing can be said of a casewhere the kick seek is performed in the outer radial direction from astate where the lens 14 is deviated in the outer radial direction.

As described above, the optical disk apparatus according to the firstembodiment of the invention calculates a feed shifting amount on thebasis of the lens offset just before the start of kick seek, thedirection of the kick seek and the number of tracks on an optical diskby which the lens is moved at the kick seek, and subsidiarily moves thefeed by the feed shifting amount in concurrence with the kick seek.Therefore, the lens is located at the center in the housing of thepickup after the kick seek, whereby subsequent tracking can be performedstably.

Further, according to the optical disk apparatus of the first embodimentof the invention, the absolute value of the compensation amount issmaller than the absolute value of the reference feed shifting amount.Therefore, at the kick seek, the lens does not move in a directionopposite to the direction along which the pickup moves, and the relativevelocity between the lens and the pickup is reduced, thereby realizingmore stable tracking.

Further, in the optical disk apparatus according to the first embodimentof the invention, the compensation coefficient at the calculation of thecompensation amount is proportional to the number of kick seek tracks.Therefore, when the number of kick seek tracks is small and the seekoperation is continued, the feed shifting amount is adjusted accordingto the number of kick seek tracks, and vibrations or resonance of themechanism caused by subsidiarily moving the feed more than the lensdeviation by kick seek are reduced, resulting in more stable tracking.

(Embodiment 2)

FIG. 4 is a block diagram illustrating a means for calculating a feedshifting amount of an optical disk apparatus according to a secondembodiment of the present invention. In the figure, numeral 43 denotes anumber-of-feed-seek-tracks calculating means for calculating the numberof tracks by which the lens is moved at feed seek before kick seek. Thisis implemented by software in the CPU.

A kick seek direction judging means 2, a number-of-kick-seek-trackscalculating means 3, a compensation amount calculating means 4, areference feed shifting amount calculating means 5, and a feed shiftingamount calculating means 6 in the optical disk apparatus according tothe second embodiment are the same as those denoted by the samereference numerals in the optical disk apparatus according to the firstembodiment.

Next, the operation will be described.

The kick seek direction judging means 2 judges whether the direction ofkick seek is an inner radial direction or an outer radial direction onthe basis of the current position and a target position of the lens 14,and outputs the obtained direction to the feed shifting amountcalculating means 6. The number-of-feed-seek-tracks calculating means 43calculates the number of feed seek tracks that corresponds to a movingdistance of the lens 14 on the basis of positions of the lens 14 beforeand after the feed seek, and outputs the obtained number to thecompensation amount calculating means 4, just before the kick seekstarts. On the other hand, the number-of-kick-seek-tracks calculatingmeans 3 calculates the number of kick seek tracks that corresponds to amoving distance of the lens 14 on the basis of the current position andthe target position of the lens 14, and outputs the obtained number tothe reference feed shifting amount calculating means 5 and thecompensation amount calculating means 4, just before the kick seekstarts. The reference feed shifting amount calculating means 5calculates a reference feed shifting amount on the basis of the numberof kick seek tracks and outputs the obtained amount to the feed shiftingamount calculating means 6. The compensation amount calculating means 4calculates a compensation amount by multiplying a coefficient which isproportional to the number of kick seek tracks by the number of feedseek tracks, and outputs the calculated compensation amount to the feedshifting amount calculating means 6. The feed shifting amountcalculating means 6 adds the compensation amount and the reference feedshifting amount in the case of kick seek in the inner radial direction,while subtracting the compensation amount from the reference feedshifting amount in the case of kick seek in the outer radial direction,thereby calculating a feed shifting amount. When the calculated feedshifting amount is smaller than 0, the feed shifting amount is outputtedas 0.

Therefore, in the CPU 21 as a whole, assuming that “F” is the feedshifting amount, “F0” is the reference feed shifting amount, “track” isthe number of feed seek tracks, “β” is the coefficient (β=κT), “κ” isthe coefficient, “T” is the number of kick seek tracks, the feedshifting amount has no polarity, and the polarity of the track is “−” inthe inner radial direction and “+” in the outer radial direction, thefeed shifting amount at kick seek is decided by the followingexpressions:

-   -   In the case of kick seek in the inner radial direction        -   F=F 0+β track (F=0, when F 0+β track<0)    -   In the case of kick seek in the outer radial direction        -   F=F 0−β track (F=0, when F 0−β track<0)

Next, the functions will be described with reference to FIGS. 5 and 6.

FIGS. 5( a)–5(c) are diagrams for explaining a case where kick seek isperformed in the outer radial direction from a state where feed seek inthe outer radial direction is ended, in which FIG. 5( a) shows a statebefore kick seek, FIG. 5( b) show a state after kick seek by thereference feed shifting amount, and FIG. 5( c) shows a state after kickseek by the feed shifting amount.

When acceleration or deceleration of the feed seek is excessive, themovement of the feed may remain as the inertia even after the feed seekis ended. In this case, when the kick seek by the reference feedshifting amount is performed, the amount of subsidiary movement of thefeed becomes excessive and the lens 14 is deviated according to theamount of movement of the lens 14 at the kick seek, as shown in FIG. 5(b). On the other hand, in the optical disk apparatus according to thesecond embodiment, the feed shifting amount F is smaller than thereference feed shifting amount F0 (0<F<F0). Thus, the lens 14 is locatedat the center of the pickup 13 as shown in FIG. 5( c). The same thingcan be said of a case where the kick seek is performed in the innerradial direction from a state where feed seek in the inner radialdirection is ended.

FIGS. 6( a)–6(c) are diagrams for explaining a case where the kick seekis performed in the inner radial direction from a state where feed seekin the outer radial direction is ended, in which FIG. 6( a) shows astate before kick seek, FIG. 6( b) shows a state after kick seek by thereference feed shifting amount, and FIG. 6( c) shows a state after kickseek by the feed shifting amount.

In a case where the movement of the feed remains as the inertia evenafter the feed seek is ended, when the kick seek by the reference feedshifting amount is performed, the amount of feed movement caused by theinertia and the reference feed shifting amount cancel each other, andthe lens 14 is deviated according to the amount of movement of the lens14 at the kick seek, as shown in FIG. 6( b). On the other hand, in theoptical disk apparatus according to the second embodiment, the feedshifting amount F is larger than the reference feed shifting amount F0(0<F0<F). Thus, the lens 14 is located at the center of the pickup 13 asshown in FIG. 6( c). The same thing can be said of a case where the kickseek is performed in the outer radial direction from a state where thefeed seek in the inner radial direction is ended.

As described above, the optical disk apparatus according to the secondembodiment of the invention calculates the feed shifting amount on thebasis of the number of tracks on an optical disk by which the lens ismoved by feed seek before kick seek, the direction of the kick seek, andthe number of tracks on the optical disk by which the lens is moved bythe kick seek, and subsidiarily moves the feed by the feed shiftingamount in concurrence with the kick seek. Therefore, the lens is locatedat the center in the housing of the pickup after the kick seek even whenthe movement of feed seek remains as the inertia, whereby subsequenttracking can be stably performed.

Further, in the optical disk apparatus according to the secondembodiment of the invention, the absolute value of the compensationamount is smaller than the absolute value of the reference feed shiftingamount. Therefore, the lens does not move in a direction opposite to thedirection along which the pickup moves at the kick seek, and therelative velocity between the lens and the pickup is reduced, resultingin more stable tracking.

Further, in the optical disk apparatus according to the secondembodiment of the invention, the compensation coefficient at thecalculation of the compensation amount is proportional to the number ofkick seek tracks. Therefore, when the number of kick seek tracks issmall and the seek operation is continued, the feed shifting amount isadjusted according to the number of kick seek tracks, and vibrations orresonance of the mechanism caused by subsidiarily moving the feed morethan the lens deviation by kick seek are reduced, thereby realizing morestable tracking.

(Embodiment 3)

FIG. 7 is a block diagram illustrating a means for calculating a feedshifting amount of an optical disk apparatus according to a thirdembodiment of the present invention. In the figure, numeral 71 denotes apost-feed-seek offset calculating means for calculating an offset of alens after feed seek, and this is implemented by software in the CPU.

A pre-kick-seek offset calculating means 1, a kick seek directionjudging means 2, a number-of-kick-seek-tracks calculating means 3, acompensation amount calculating means 4, a reference feed shiftingamount calculating means 5 and a feed shifting amount calculating means6 in the optical disk apparatus according to the third embodiment arethe same as those denoted by the same reference numerals in the opticaldisk apparatus according to the first embodiment.

Next, the operation will be described.

Just after the feed seek is ended, the post-feed-seek offset calculatingmeans 71 receives data of the quantity of deviation of the lens 14 fromthe center of the housing of the pickup 13 from the analog front end IC18, A/D-converts the data, thereby calculating an offset after the feedseek, and outputs the calculated offset to the compensation amountcalculating means 4. Just before the kick seek starts, the pre-kick-seekoffset calculating means 1 receives data of the quantity of deviation ofthe lens 14 from the center of the housing of the pickup 13 from theanalog front end IC 18, A/D-converts the data, thereby calculating anoffset before the kick seek, and outputs the calculated offset to thecompensation amount calculating means 4. Simultaneously, the kick seekdirection judging means 2 judges whether the direction of the kick seekis an inner radial direction or an outer radial direction on the basisof the current position and a target position of the lens 14, andoutputs the obtained result to the feed shifting amount calculatingmeans 6. On the other hand, the number-of-kick-seek-tracks calculatingmeans 3 calculates the number of kick seek tracks that corresponds to amoving distance of the lens 14 on the basis of the present position andthe target position of the lens 14, and outputs the obtained number tothe reference feed shifting amount calculating means 5 and thecompensation amount calculating means 4, just before the kick seekstarts. The reference feed shifting amount calculating means 5calculates a reference feed shifting amount on the basis of the numberof kick seek tracks and outputs the amount to the feed shifting amountcalculating means 6. The compensation amount calculating means 4calculates a compensation amount by multiplying a difference between theoffset before the kick seek and the offset after the feed seek by acoefficient which is proportional to the number of kick seek tracks, andoutputs the compensation amount to the feed shifting amount calculatingmeans 6. The feed shifting amount calculating means 6 adds thecompensation amount and the reference feed shifting amount in the caseof kick seek in the inner radial direction, while subtracting thecompensation amount from the reference feed shifting amount in the caseof kick seek in the outer periphery direction, thereby calculating afeed shifting amount. When the calculated feed shifting amount issmaller than 0, the feed shifting amount is outputted as 0.

Therefore, in the CPU 21 as a whole, assuming that “F” is the feedshifting amount, “F0” is the reference feed shifting amount, “offset1”is the offset after the feed seek, “offset2” is the offset before thekick seek, “δ” is the coefficient (δ=εT), “ε” is the coefficient, “T” isthe number of kick seek tracks, the feed shifting amount has nopolarity, and the polarity of the offset is “+” in the inner radialdirection and “−” in the outer radial direction, a feed shifting amountat the kick seek is decided by the following expressions:

-   -   In the case of kick seek in the inner radial direction        F=F 0+δ (offset2−offset1) (F=0, when F 0+δ(offset2−offset1)<0)    -   In the case of kick seek in the outer radial direction        F=F 0−δ (offset2−offset1) (F=0, when F0−δ (offset2−offset1)<0)

Next, the functions will be described with reference to FIGS. 8 and 9.

FIGS. 8( a)–8(c) are diagrams for explaining a case where the kick seekis performed in the outer radial direction from a state where a movementdue to the inertia remains even after the feed seek in the outer radialdirection is ended, in which FIG. 8( a) shows a state before the kickseek, FIG. 8( b) shows a state after kick seek by the reference feedshifting amount, and FIG. 8( c) shows a state after kick seek by thefeed shifting amount. In the figure, numeral 83 denotes a position ofthe pickup just before the kick seek starts and numeral 85 denotes aposition of the pickup just after the feed seek is ended, and FIG. 8( a)shows a case where the feed is moved due to the inertia in a short timefrom the end of feed seek till the start of kick seek.

When acceleration or deceleration of the feed seek is excessive, themovement of the feed may remain as the inertia even after the feed seekis ended. In this case, when kick seek by the reference feed shiftingamount is performed, the amount of a subsidiary movement of the feed isexcessive and the lens 14 is deviated as shown in FIG. 8( b). On theother hand, in the optical disk apparatus according to the thirdembodiment, the feed shifting amount F is smaller than the referencefeed shifting amount F0 (0<F<F0). Thus, the lens 14 is located at thecenter of the pickup 13 as shown in FIG. 8( c). The same thing can besaid of a case where the kick seek is performed in the inner radialdirection from a state where the feed seek in the inner radial directionis ended.

FIGS. 9( a)–9(c) are diagrams for explaining a case where kick seek isperformed in the inner radial direction from a state where a movementdue to the inertia remains even after feed seek in the outer radialdirection is ended, in which FIG. 9( a) shows a state before kick seek,FIG. 9( b) shows a state after kick seek by the reference feed shiftingamount, and FIG. 9( c) shows a state after kick seek by the feedshifting amount. In the figure, numeral 93 denotes a position of thepickup just before the kick seek starts and numeral 95 denotes aposition of the pickup just after the feed seek is ended, and FIG. 9( a)shows a case where the feed is moved due to the inertia in a short timefrom the end of feed seek till the start of the kick seek.

In a case where the movement of the feed remains as the inertia evenafter the feed seek is ended, when kick seek by the reference feedshifting amount is performed, the amount of feed movement due to theinertia and the reference feed shifting amount cancel each other and thelens 14 is deviated according to the amount of movement of the lens 14at the kick seek, as shown in FIG. 9( b). On the other hand, in theoptical disk apparatus according to the third embodiment, the feedshifting amount F is larger than the reference feed shifting amount F0(0<F0<F). Thus, the lens 14 is located at the center of the pickup 13 asshown in FIG. 9( c). The same thing can be said of a case where the kickseek is performed in the outer radial direction from a state where feedseek in the inner radial direction is ended.

As described above, the optical disk apparatus according to the thirdembodiment of the invention calculates a feed shifting amount on thebasis of the lens offset just before kick seek starts, the lens offsetjust after the end of feed seek before the kick seek, the direction ofthe kick seek and the number of tracks on an optical disk by which thelens is moved by the kick seek, and subsidiarily moves the feed by thefeed shifting amount in concurrence with the kick seek. Therefore, thelens is located at the center in the housing of the pickup after thekick seek even when the movement of feed seek remains as the inertia,whereby subsequent tracking can be performed stably.

Further, in the optical disk apparatus according to the third embodimentof the invention, the absolute value of the compensation amount issmaller than the absolute value of the reference feed shifting amount.Therefore, the lens does not move in a direction opposite to thedirection of the pickup movement at the kick seek and the relativevelocity between the lens and the pickup is reduced, thereby realizingmore stable tracking.

Further, in the optical disk apparatus according to the third embodimentof the invention, the compensation coefficient at the calculation of thecompensation amount is proportional to the number of kick seek tracks.Therefore, when the number of kick seek tracks is small and the seekoperation is continued, the feed shifting amount is adjusted accordingto the number of kick seek tracks, so that vibrations or resonance ofthe mechanism caused by the subsidiary movement of the feed larger thanthe lens deviation by the kick seek are reduced, resulting in morestable tracking.

APPLICABILITY IN INDUSTRY

As described above, the optical disk apparatus according to the presentinvention is suited to perform stable tracking.

1. An optical disk apparatus for moving a feed when data is read from anarbitrary position on an optical disk surface, thereby performing atracking control, said optical disk apparatus comprising: anumber-of-feed-seek-tracks calculator operable to calculate a number oftracks on an optical disk by which a lens is to be moved by a feed seekbefore a kick seek; a kick seek direction judger operable to judgewhether a direction of the kick seek is an inner radial direction or anouter radial direction on the basis of a current position and a targetposition of the lens just before the kick seek starts; anumber-of-kick-seek-tracks calculator operable to calculate a number oftracks on an optical disk by which the lens is moved by the kick seek; areference feed shifting amount calculator operable to calculate areference feed shifting amount on the basis of the number of trackscalculated by said number-of-kick-seek-tracks calculator; a compensationamount calculator operable to calculate a compensation amount bymultiplying the number of tracks calculated by saidnumber-of-feed-seek-tracks calculator by a compensation coefficient; afeed shifting amount calculator operable to add the compensation amountand the reference feed shifting amount when the direction is judged tobe the inner radial direction by said kick seek direction judger, and tosubtract the compensation amount from the reference feed shifting amountwhen the direction is judged to be the outer radial direction, therebycalculating a feed shifting amount; and a controller operable tosubsidiarily move the feed by the feed shifting amount in concurrencewith the kick seek.
 2. The optical disk apparatus as defined in claim 1,wherein said compensation amount calculator is operable to set thecompensation amount such that a direction of reference feed shiftingdoes not change when the compensation amount is added to or subtractedfrom the reference feed shifting amount by said feed shifting amountcalculator.
 3. The optical disk apparatus as defined in claim 1, whereinsaid compensation amount calculator is operable to calculate thecompensation amount such that the compensation coefficient isproportional to the number of tracks calculated by saidnumber-of-kick-seek-tracks calculator.